I have not seen or tried the ultrasonic, but i have a isonic 127 and is really fast for a 85cm wide board. I mean.. .REALLY fast. The ultrasonic maybe more comfy, and perhaps easier to gybe, but i think the 127 will be faster.

Im similar weight/height, 98kg 194cm. For me, iS107 and iS137 works very well. But I do have a Formula 161 as well.

But to be honest, these days I don't use the F161 much because in 8k to 11k I can get going on the iS137 with my 9.5m and 51cm fin and feel nicely powered.

For me, the iS137 just feels way more exciting c/w formula. If the wind is always under 9/10k, then Formula is easier, and the US147 would be a real option.

If I did not have an F161, then I would probably go US147/iS107 as Im happy to take the 8k to 10k winds as well.

I guess the answer to your question is: If you sail in an area with steady 8k to 11k winds and have a 9.5m race sails, then iS127/137 and a grunty fin will be a best fun/fast. If the winds are less, take the US147.

I understand that the thin hull on the US147 give great control in medium winds, so like the iS127/137, control if the wind pick up will not be a big problem.

Don't rule out the heavy weights iS137, its flat vee to flat hull works great for heavier guys and also allows you run fins down to 45cm in medium/highish winds, and it flys confidently over chop. Today I got over 34k peak with an 8.6m/47cm fin. So it's fast for sure

It's depend also of your use, Slalom Racing go for 127/137 this the higher performances you can get at 85cm wide but if you wan to plane in very light winds ot of the slalom rules then UltraSonic will be the best. Performances of a Formula in planning but much more easier and faster also on reach under 11 Knots. So with this you can choose the best board for you.

In 8-12 "steady" conditions, the IS127 and IS137 could be good, I think.

But I definitely chose for the Ultrasonic just because the word "steady" is not compatible with our lakes next to the sea (e.g. Grevelingen & veerse meer) in these conditions. When I'm surfing on one of those 2 lakes, I always experience a lot of lulls and then I'm glad to have a board like the US147 that nicely planes trough it, points very high and always brings me back to my starting point.

It's different on the open sea, where you have the wind much more steady.

Oh and don't be afraid of the US147 when the wind picks up. It's rock stable and bloody fast. It really feels like a slalom board, much more than a Formula. I sold my F161 without any regrets.
Another advantage for me in very light wind is that I don't need to pump it onto the plane. But I suppose that's because I'm getting too old